The present invention relates to an acceleration sensor, more specifically, to an acceleration sensor, which, for example, is attached to an inclining member such as a seatback of a vehicle, and detects acceleration of the vehicle without being affected by an inclination of the inclining member.
An acceleration sensor for detecting acceleration of a vehicle or the like may include a sensor ball of predetermined mass disposed on a supporting surface of a supporting body such as a bracket, which sensor ball (moving body) inertially moves due to an acceleration at or above a predetermined value so as to drive an output member, and the sensor thereby detects the acceleration.
In a case in which this type of acceleration sensor is attached to an inclining member such as a seatback of a vehicle, the supporting surface of the bracket needs to be maintained at a predetermined angle so that the acceleration sensor can detect the predetermined acceleration even when the seatback is in a reclining position.
Accordingly, for example, a so-called dead load follow-up type of acceleration sensor, in which the bracket is rotatably supported around an axis which is parallel to a center of rotation of the seatback, a weight is attached below the axis, and, because of the load of the weight, the supporting surface of the bracket is maintained at a predetermined angle regardless of a reclining angle, has been suggested. However, the dead load follow-up type of acceleration sensor operates in the same manner when the seatback is inclined as when the entire vehicle is inclined. Therefore, if the acceleration sensor is set to not operate when the seatback is considerably inclined, the acceleration sensor does not operate when the entire vehicle is considerably inclined either (a so-called tilt lock angle is large).
On the other hand, a so-called linking follow-up type of acceleration sensor, in which a portion of a seat of the vehicle is connected to the bracket by a connecting member such as a wire and, when the seatback is inclined, the bracket is forcedly rotated by the connecting member and the supporting surface of the bracket is maintained at the predetermined angle, has been suggested. However, in the linking follow-up type of acceleration sensor, irregularities in the angle of forced rotation of the bracket are caused by slight deformations of the connecting member (for example, in a case in which a wire is used as the connecting member, a twist in the wire), slight looseness of a portion of the connecting member which is attached to the seat, and the like, and the supporting surface of the bracket cannot be maintained at the predetermined angle.
In consideration of such facts, an object of the present invention is to obtain an acceleration sensor which can always maintain a supporting body at a predetermined angle even if an inclining member is inclined and, moreover, in which a tilt lock angle is small.
In the invention described in claim 1, an acceleration sensor comprises: a supporting body attached to an inclinable inclining member, which supporting body can rotate at least around an axis that is parallel to a center of inclination of the inclining member; a moving body supported to the supporting body, which moving body inertially moves due to an acceleration at or above a predetermined value applied to the supporting body, and drives an output member; a mass body, which, by a weight of the mass body, applies torque to the supporting body to a direction such that the supporting body has a predetermined angle with respect to a horizontal plane; and a rotating member, which followingly moves in accordance with an inclination of the inclining member, and enables the supporting body to be independently rotated within a predetermined range by the torque from the mass body such that the supporting body has the predetermined angle with respect to the horizontal plane.
When the inclining member is inclined, the supporting body receives torque from the mass body, and attempts to rotate in a direction in which the supporting body has a predetermined angle with respect to the horizontal plane. Because the rotating member rotates in accordance with the inclination, the supporting body rotates to the predetermined angle. When an acceleration at or above the predetermined value is applied to the supporting body in this state, the moving body inertially moves and drives the output member, and the acceleration is detected. The rotation of the supporting body, which is independent of the rotating member, is limited within the predetermined range by the rotating member. Thus, the acceleration sensor operates only when an acceleration at or above the predetermined value occurs or the entire vehicle is inclined, and the acceleration sensor does not operate when only the inclining member is inclined. Accordingly, a so-called tilt lock angle can be small.
Because of the rotating member, the supporting body can rotate independently of the rotating member within a predetermined range when the supporting body receives torque from the mass body. Therefore, even if an irregularity in follow-up movements of the rotating member with respect to the inclining member occurs due to, for example, looseness of a portion of the supporting body which is attached to the inclining member, deformation of the rotating member or the like, the supporting body rotates, due to the torque received from the mass body, in a direction in which the supporting body has a predetermined angle. Accordingly, the irregularity in follow-up movement of the rotating member is corrected and the supporting body has the predetermined angle with respect to the horizontal plane.
In the invention described in claim 2, according to the invention described in claim 1, the rotating member comprises: a wheel, which can rotate coaxially with the supporting body, and which rotates at a predetermined angle in accordance with an angle of inclination of the inclining member; a first abutting body provided so as to protrude from the wheel toward the supporting body; and a second abutting body provided so as to protrude from the supporting body toward the wheel, the first and second abutting bodies forming a predetermined clearance, and which second abutting body enables the supporting body to rotate independently of the rotating member within the clearance.
When the inclining member is inclined, the wheel rotates the predetermined angle in accordance with the angle of inclination. Thus, the first abutting body of the wheel followingly rotates with respect to the second abutting body of the supporting body, which attempts to rotate due to the torque from the mass body. Accordingly, the supporting body is allowed to rotate, and the supporting body has the predetermined angle with respect to the horizontal plane.
The predetermined clearances are formed between the first abutting body and the second abutting body. Therefore, even if a variation in a following angle of the first abutting body occurs when the inclining member is inclined, if the variation is within the clearances, the supporting body receives the torque from the mass body and rotates, and the supporting body has the predetermined angle with respect to the horizontal plane.
In this manner, due to a simple structure in which the first abutting body is provided at the wheel and the second abutting body is provided at the supporting body, even if a variation in a following angle (follow-up movement) of the first abutting body occurs, the supporting body can have the predetermined angle with respect to the horizontal plane.